1. Field of the Invention
Aspects of the present invention generally relate to a closed-loop multi-antenna system, and more particularly, to an apparatus and method for transmitting and/or receiving data in a closed-loop multi-antenna system.
2. Description of the Related Art
Compared to a wired channel, a wireless channel environment generally has low reliability due to multipath interference, shadowing, propagation attenuation, time-variant noise, and interference. As a result, an increase of data transmission rates in mobile communications has been impeded.
A Multiple Input Multiple Output (MIMO) system has been proposed to avert the aforementioned problems. A MIMO system is an example of a multi-antenna system. Multi-antenna systems support a single-user mode and a-multi-user mode. In the single-user mode, data is transmitted to one user through a plurality of transmit antennas. In contrast, in the multi-user mode, data is transmitted to a plurality of users through the transmit antennas.
The multi-antenna systems are also categorized as closed-loop systems relying on feedback information for resource allocation and open-loop systems that do not use feedback information for resource allocation. Efficient resource allocation with minimal feedback information is a critical task of a closed-loop multi-antenna system. In particular, when multiple users are supported, decreasing the amount of feedback information is more significant.
Meanwhile, due to a diversification of wireless communication services, there is a high probability that mobile stations (MSs) or terminals with different characteristics co-exist in the same service area. Hence, a base station (BS) should be able to support different communication schemes. For example, the BS should be able to support both the single-user mode and the multi-user mode. The BS should also be able to support both types of MSs using linear signal detection and non-linear signal detection.